Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$166.58	3.842%	$172.98	$172.98	$173.00	$173.00
Purchase #2	$218.52	10.796%	$242.1114	$242.11	$242.10	$242.10
Purchase #3	$62.40	7.274%	$66.939	$66.94	$66.95	$66.90
Purchase #4	$52.56	12.690%	$59.2299	$59.23	$59.25	$59.20
Purchase #5	$65.32	8.119%	$70.6233	$70.62	$70.60	$70.60
Purchase #6	$192.42	4.532%	$201.1405	$201.14	$201.15	$201.10
Purchase #7	$167.89	12.441%	$188.7772	$188.78	$188.80	$188.80
7 purchase totals =	$925.69		$1,001.8013	$1,001.80	$1,001.85	$1,001.70